Process of purifying arsenious chloride



Own, 1924. v

' E. w. 'wEscoTT PROCESS OF PUR'IFYING ARSEN IOUS CHLORIDE Filed March so. 1921 sheet -shed [EM/Vassar]:-

Oct. 21, 1924- 1,512,734 E. W. WESCOTT PROCESS OF PURIFYING ARSENIOUS CHLORIDE Filed march 50. 1921' 2- Sheets-Shea; 2

llllllllllllllllllll I lllilllllllllll 92 Gi i Patented Oct. 21, 1924.

' UNITED-STATES ATENT- oFFicE.

ERNEST W. WESCO'I'T, 0F NIAGARA. FALLS, NEw YORK, ASSIGNOR, 'IBY ME SNE ASSIGN- MENTS, TO METALLURGIQAL DEVELOPMENT COMPANY, OF BOSTON, MASSA- CEUSETI'S, A COBPPPATION OF MASSACHUSETTS.

PROCESS OF PURIFYING ABSENIOUS CHLORIDE.

Application filed March 30, 1921. Serial No. 456,940.

To all whom it may concern:

Be it known that I, Enm:s'r W. Wrsco'r'r, a citizenof the United States, residing at Niagara Falls, in the county of Nia 'ara and State of New York, have invented certain new and useful Improvements in Processes of Purifying Arsenious Chloride, of which the following is a specification.

This invention relates to processes of purifying arsenious chloride, and it comprises a method of' purifying arsenious chloride formed by the action of chlorin on arscnid ores and speisses wherein the vapors coming from the chloridizing operation are cooled to about 150 C. to condense ferric chloride and are further cooled to condense A561 the condensed AsCl being then treated to remove contained sulfur, residual iron,-

etc, as by scrubbing with concentrated HCl solution or by heating with A5 0,; all as more fully hereinafter set forth and as claimed. X

Certain arsenid ores of cobalt and other metals, as well as speisses, are difiicult of treatment by the ordinary metallurgical processes because of the presence of arsenic. These ores however may be readily freed of arsenic by a treatment with chlorin while in a heated condition, the chlorin converting the arsenic into a volatile chloride (AS013) which goes forward as vapor. The action of the chlorin evolves much heat and with rich ores and speisses is usually sufficient to keep up the action. Ordinarily, in practical opcration a fine ground ore passing through a rotary drum is treated in counter-current with a flow of chlorin from a suitable source, such as the gas from electrolytic cells producing caustic soda. Cobalt, nickel, copper,

silver, etc, are converted into fixed or nonvolatile chlorids, which canafterwards be readily worked up by methods not here important, while the arsenious chloride goes forward as vapor. If the ores or speisses contain sulfur, sulfur chloride also goes forward with the arsenic. More or less ferric chloride occurs in the vapors when the ore contains iron, as it usually does. The vapors also usually contain more or.less free chlorin, ore dust, etc. It is the purpose of the present invention to provide a simple,

ready and economical method of producing a relatively pure arsenious chloride from the products of such a metallurgical operation.

Inthe present method I cool the gases and vapors coming from the chloridizing apparatus 1n two stages; the first being to a temperature near but above the boiling point of AsCl (134 C.) while the second is at a lower temperature.' In the first cooling, I

ordinarily carry the temperature down to about 150? 0.1 This condenses most of the ferric chloride and with it comes down such dust as-may be present. Cooling is best performed in a metal shell provided with internal means, such as scraper and conveyor,

to remove condensed matter. In the second cooling, it is best to usea 'sort of rectifying condenser provided with suitable cooling means to keep it at'tenip'eratures at which the eaterpart of the arsenious chloride will liquefy. The condensate contains in addition to AsCl, minor amounts of ferric chloride and, if the original ore or speiss carried sulfur, more or less sulfur chloride. Much of the sulfur chloride, if present, however, goes on beyond this condenser. While the boiling point of sulfur chloride (138 C.) is not far from that of arsenious chloride, in the presence of free chlorin its volatility increases; and the greater the proportion of chlorin in the eilluent vapors and gases from the chloridizing apparatus, the greater is the tendency of sulfur chloride to go past the AsCl condenser.

The crud=liquid arsenious chloride rccovcred in the second condensation still carrics some iron and sulfur. It may be treated in either of two ways: .ne dcsirableonc depending largely'upon the amount of sulfur present. If the arsenious chloride be low insulfur, it may be simply scrubbed in counter-current with ordinary concentrated muriatic acid, that is to say, a strong solution of HCl in water (hydrochloric acid). This abstracts the iron and some or all of the sulfur. Or instead of treating in counter.- current, concentrated hydrochloric acid and liquid arsenious chloride may be simply stirred together and then allowed to separate. There the arsenious chloride is originally low in sulfur, the amount of sulfur so removed maybe sufiicient to give the de- "sired degree of purity. In the event'that the removal'of-sulfur in this wa of operating-isinot s ufiicienhas may be t e case with I 6 ores or speisses rich in sulfur, the scrubbed .AsGl, may next be treated with white ars i z sl- I a Sulfur Chloride reacts energetically with As,O formingarsenious chloride, fne'esulfor and gaseous S0,; It is in general; ad-

visable to mix the arsenious chloride'ivhich is to be freed from sulfur chloride with 111- ble amount of sulfur chloride present, during the period of energetic reaction there is a free escape of SO as gas which,of course,

carries forward more or chloride. The treatment is best effected in ,39, an apparatus fprovided with a reflux condenser to return volatilized A501, as far as possible. The reflux condenser is useful during this stage as well as du'rmgthe final boiling; Instead of first scrubbing with strong hydrochloric acid solution and then heating' with white arsenic, the l quid AsCl, may be heated with 'As O in the first place. This results, as before, in breaking up the sulfur chloride. 4 0 Aftenthe treatment .with white arsenic. the AsGl may be simply cooled and filtered or decanted from the insoluble sulfur, iron compounds, etc. .But it is better, as a rule, to redistil it; which. maybe done in tho. 'same vessel or in another. The redistilled A'sCl is substantially pure.

-In the accompanying illustration lhare shown, more or less diagrammatically, certain organizations of apparatus elements convenient inthe performance of the described process: i

Figure 1 is a vertical longltudmalseci n through a chlorinating apparatus and condenser; Figure 2-is a view partly in section and partly in /elevation of the/scrubber chambers, still and condensers, and should .beread as a continuation of Figure 1; and Figure 3 is a detailed segmental section of I the scrubber showing'the plates. The difler- '60 ent elements are notin proportion.

In the apparatus shown ore passes from I hopper 1 into a rotary'reaction chamber 2 by means of screw conveyor 3. Chlorm from inlet 5 passes through a stationary fur B5 nace head 6 into the reaction chamber. The

- down' the discharge pi less arsenious fixd chlorids formed by chlorinating 'the ore are discharged through a conduit 8.,

The aseous, products of reaction pass throng v the stationary furnace head 4 and '7 into the'- ferric chloride condenser 9, w ich is fitted withthe oil jacketv 10. maintainedat about 1509 C. The uncondensed vapors of arsenic chloride, sulfur chloride, etcQ, pass; through the connection 11 into the arsenic chloride con ,denser 12 fitted with the water cooling.- ]acket 13. The shaft 14 driven through pullley or sprocketwheel 15 passes t r0 1 the condensers 9 and 12, being'sealed y the stufi'ing'boxes 16. The shaft 14 carries the ribbon serew conveyor 1'2'," which discharges condensed ferric chloride through the discharge pi e19, and a'ribbon screw conveyor 18, which cleans the walls of the arsenic chloride condenser 12 from any ferric chloride, etc., whichmay reach these walls, and discharges this material together with the condensed arsenic chloride through the discharge pipe 20. Unconden'sable gasespass oif to the scrubbing means not shown through 21.

The crude arsenicchloride passes into the receiver 22 and may be drawn therefrom through the valve 23 and-the rosette or dis trihuting head 24 located within the duriron or other acid-proof washing chamber 25.

Within ,this tower-like tank the arsenic chloride stands at a level 26, in virtue of the position of the goose-neck dischar e 31'. Commercial crude hydrochloric 801d,' or

other forms of HCl obtained as a by-prod-- uct from the manufacture ofAs o 1s introduced through the inlet 27 under sufiicient hydrostatic head to cause it to pass into the tank 25 against the hydrostatic head of arsenic chloride therein. The hydrochloric acid rises against the corrugated packing members 28, filling the circular corrugations on the same and overflowing upwards against the corrugated annular pack;

ing members 29. The detail of members 28 and 29 is' shown (in Fig.3). Thepackingi members are supported and-spaced by lugs not shown and are made of duriron or acid-proof stoneware. lt is to be noted that crude concentrated l'lC-l saturated with arsenic chloride is practically without efl'ect on iron, but it is nevertheless desirable tomake the apparatus acid-proof so that the dilute solu'- tions occurring when the ap aratus is,

the other. Such particles, which are formed when the'two liquids are violently agitated together separate very slowly.

- The arsenic chloride which has been'admitted throughi 24 having thus been thoroughly washed .in counter-current, passes through 31 into the receiver 32,1fromjwhich it maybe removed for use by the discharge 33 or drawn into the still 37 the discharge 34. i

The still ischarged with crude arsenic chloride through the inlet 36 or with partiall purified arsenic; chloride through. 34

. as a 'vementioned. The still 37 is fitted with an internal scra r 38 driven by means not shown and provi ed with a stufi'in box 40. The heating means for this still'are not shown. Arsenic oxide is admitted to the still from the gated hopper 43 through the dome' 42- which is fitted with pyrex glass pots (not shown) for the observation of frothin still pass out t rough the dome 42 and through the pipe 44 into the condenser 45 furnished with internal water cooling coils.

Condensed liquid-- chloride may be refluxed back to 37 through valved pipe 47 or ma be sent directly to storage tank 46 throu h valved pipe 45. Where the arsenious c ride is finally redistilled the vapors pass through 44, 45 and 45 to 46 whence the contion of a solution of HCl and a depositof ris O. in a modified form of my in- \EliillOIl I treat the liquid arsenious chloride with a small amount of water; sy, or for-a per cent, and heat at say 50' time, thereby breaking up the sulfur chloride with production of sulfur and S0 and removing iron in the HCl solution. After the digestion, the liquids (arsenious chloride and muriat-ic acid) may be allowed,

to cool and separate. -The arsenious c1110- rizhr may be used as it is or may be rcdis-- tilled.

In scrubbing the arsenious chloride with HCl solution (nnu-iatic acid), it is possible and advantageous to use acid formed. in vario'is processes of working up arseniby means of The vapors from the .ing anarsenid ore witli c to liquefy A'sCl washing the MCI, with aqueous H01 .to remove ironand sulfur,

ous chloride to convert it into other commercialmaterials. In one such method, for example, -arsenious chloride is caused to react with a limited amount of water in the presence of chlorin, thereby producing a. hotsolution of arsenic acid and vapors of HCl which maybe condensed in water and used for the present purposes. Sucharsenic as may pass forward with the 1101 of course in nowise injures the acid for the present purposes and its. presence is indeed beneficial in. the HCl-scrub.

What I claim is 1. In' the manufacture of arsenious chloride, the process which comprises chloridizing an arsenid ore with chlorin at'a. high temperature, cooling the resultant gases and vapors to a temperature near but above the liquefying point of AsCl and removing condensed ferric chloride ,and dust, further coolin to liquefy AS013, heating the liquid As 1, with AsgO to break up sulfur chloride and redistilling the AsCl 2. In the manufacture of arsenious chloride, the process which .CGIIilSI'lSBS chloridiz orin at a high temperature; cooling the resultant gases and vapors to a temperature near but above the liquefying int of AsCl, and removing ferric chloride and dust; further. cooling heating the A501, with AS,O, to break up isgllual sulfur chloride and redistilling the 3. In the purificationjof 'AsCl containing ferric chloride and 'sulfur chloride, the process which comprises washing such A501,: with a ueous hydrochloric acid, heating KIQOiAS l, with A5 0, and redistilling the 4. In the purification of .AsCl containing sulfur clilor de'the process which comprises heating, such AsGl with A5 0 in sufiicient amount to break up the sulfur chloride present. V

5. In the purificat on of ASCII, containing sulfur-chloride the process which com rises heating such AsGl, with As,O in sufiicient amount to ireak up the sulfur chloride present and redistilling. t

6. In the purification of AS01 containing ferric chloride and sulfur chloride the process which comprises washing such AsCl with an aqueous solution of HCl.

In testimony whereof, I afiix my sig- 116 nature.

ERNEST W, wnsoorr. 

